Hydraulic stripper for punch presses



June 12, 1945. c. M EASON 2,378,068 I HYDRAULIC STRIPPER FOR PUNCH PRESSES 2 Sheets-Sheet 1 1.9 ,rlllllfl J3 ;f% 52 INVENTOR. .Clarerzcefliczsarz,

54:12am, 41221 I 0% I I Patent ed June 12, 1945" arnaamc srairrnn Fon rune-n masses Clarence M. Eason, Waukeslia, Wis. Application June 8, l9 42, Serial No. 446,311

' '1 Claims. (onus- 5o) The present invention relates to Lhydraulic stripping mechanisms for punch presses and the like.

In performing deep drawing operations in a punch press, it is frequently difficult to effect mechanical release of the drawn blank from the punch upon the completion of the drawing operation without causing excessive mutilation of the upper edge of the blank where the mechanical stripper. engages the blank. This is particularly true when performing deep drawing operations on tubular shells, such as steel cartridge cases, where the punches used in the last one or two draws have only a very slight taper and hence have a tighter binding action- Steel shells appear to be more difiicult to strip from the punches than brass shells, and it may. require the exertion of several thousand pounds pressure on the steel shell to strip it' from the last punch. When the stock has been drawn down to a shell of very thin wall, the exertion of a high stripping pressure as a mechanical force against the upper edge of this thin walled shell is very likely to mutilate the upperedge of the shell so badly as to require that a considerable portion of the upper edge of the shell be cut oil as waste scrap. This difliculty of mechanical stripping and resultant mutilation of the shells are entirely avoided by my improved hydraulic stripping mechanism.

The general object-of the present invention is to provide improved hydraulic stripping mechanism which will strip the shell from the punch by the exertion of a hydraulic pressure between the lower end of the shell and the punch.

It is'a further object of the invention to provide an improved hydraulic stripper characterized by a pressure cylinder which is arranged to respond to motion of the press ram, whereby an extremely high hydraulic pressure is only exerted for a brief interval on the shell, and whereby this hydraulic stripping pressure is-timed to occur automatically just as soon as the shell has cleared the drawing die.

Another object of the invention is to provide an improved hydraulic stripper-which is combined as a part of the conventional cooling and lubricating system which circulates the cooling" and lubricating oil between and over the die parts. A portion of this cooling and lubricating oil is utilized as the hydraulic medium in each stripping operation, and hence the same lubricating medium performs the three-fold iunctionof cooling, lubricating and stripping.

essentially limited thereto.

' tion of the punch 2| has a relatively slight taper 'inventionwill appear from the following detailed description of one preferred embodiment thereof. In the accompanying drawings illustrating such embodiment:

Figure 1 is a fragmentary vertical axial sectional view taken on a fore and aft plane through ,a conventional drawing press, showing my improved -hydraulic stripping mechanism applied thereto Figure 2 is a detail sectional view on a larger scale through the stripping mechanism; and

Figure 3 is a detail sectional view on a larger scale showing the inlet valve and associated parts at the upper end of the hydraulic cylinder.

16 Referring to Figure 1, the press is of any con- 20 from a back countershaft l2 carrying a pinion l3 which drives a large bull gear (4 at one end of the crank shaft l5. The crank on the crank shaft 'reciprocates a pitman I! which reciprocates a ram 18 upwardly and downwardly along vertical guideways formed on the side frame members 9.

The two die memberswhich perform the drawing operation are carried by the ram l8 and the stationary bolster or bed plate I9. For the purpose of illustrating a typical deep drawing operation where my improved hydraulic stripper is of greatest utility, I have shown the punch press as being equipped with a punch 2| and a die 22 adapted to perform one of the last draw- 85 ing operations on a 3'! millimeter steel cartridge case, indicated at 23. It will be understood that I have chosen this construction and arrangement of die parts primarily for the purpose of apt illustration, and. that the invention is not diminishing down towards its lower end, and the upper end of the punch is formed with a head flange 24. This flange .is clamped in matching cylindrical sockets 25 and 26 formed in the opposing faces of a punch holder 21 and a punch flange 28. The punch holder 21 may be releasably secured to the ram it through the instrumentality of an upwardly extending shank por- '50 tion 29 which is detachably anchored in the ram,

and the flange or cap' member 28 is releasably secured to the punch holder 21 by the cap screws 3|.

The circular die 22 sets in a recessed opening Other objects, features and advantages of the -12 formed in the upper surfaceof-a die shoe plate The drawing por- 33 which is suitably anchored to the bolster or bed plate I3. Seated in a recessed opening in the upper surface of the die 22 is a gauge ring 34. The throat of the drawing die 22 is formed with an upper drawing or forming. portion 22.1: where the actual drawing operation is performed, and is also formed with a lower clearance portion 221 where the upper end of the shell 23 is cleared or freed of the drawing die. Openings 35, 36 and 31 are formed in the members 34, 33 and [8, respectively, in alinement with the die throat 22a: for permitting the drawn shell 23 to be passed down through the assembly and to be ejected from the bottom side of the bolster or bed I8.

It is customary to supply a liquid coolant in the form of lubricating oil to the punch 2| and die 22 during the drawing operation, as illustrated by the inlet ducts 4| and 42 leading to the 7 cap member 28 and to the gauge ring 34. The pipe ll communicates through a lateral bore 83 with an annular discharge channel 44 formed of the cylinder and a cylindrical extension boss 81 extending upwardly from the piston. Such packing ring is preferably in the form of a Neoprene washer of substantially U-shaped crosssection. The washer or ring is maintained in proper position by an annular retainer 88 formed with a downwardly extending annular flangeii! which projects into the annular recess formed in the upper side of the packing ring 86. Upward movement of the retainer 88 along the central boss 81 is limited by; a snap type of locking ring 1| which snaps into an annular groove and against the cylinder wall, the confining ring in the-cap member 28 around the shank of the punch 2|, this channel causing the oil to flow down uniformly around the entire outer surface of the punch. The other pipe 42 similarly communicates through a lateral duct 45 with a distributing channel 48 formed in the under surface of the gauge ring 34, this channel distributing the oil uniformly down around the drawing throat 22a: and overthe exterior surfaces of the shell 23.

to be driven from the countershaft l2 in any length, to accommodate the vertical movement of the punch and ram. The pump 48 draws its supply through a suction pipe which leads down to a strainer and foot valve 52 located'in an oil sump 53 which may be recessed into the floor below the base of the punch press, whereby overflow of the oil occurs back into the sump.

Referringnow to the hydraulic stripping mechanism, this comprises a hydraulic'cylinder 55 which is secured directly to the under sideof the rain l8, preferably in rear of the punch 21, as shown in Figure 1. The upper end of the cylinder screws into a mounting base 58 which is bolted to the under surface l8 of the ram 18. A retainer cap 51 screws over the lower end of the hydraulic cylinder 55 for retaining the pis-. ton 58 from outward displacement at the lower end of the cylinder. The piston is formed with a reduced extension 58 passing down through the aperture in the cap 51, and provided with a striking head 8| at its lower end. This striking head 8| is adapted to strike theupper surface 33' of the die shoe 33 substantially at that instant in the downward stroke of the ram i8 when the punch 2| has drawn the upper end of the shell 23 just past the drawing throat 22.1: and into the clearance space 2211. If deslred,,-,the striking head 6| may be composed ofrelatively hard rubber fiber or other material effective to minimize the noise ofrimpact. A compression I spring 63 normally tends to hold the piston 58 at the bottom of its stroke against the closure ring 51, the upper end of this spring beingseated in a counterbore 84 in the mounting base 58 and the lower end of the spring extending down into a central bore 85 formed in the Piston 58.

The upper end of the piston 58carries a packing ring 86 which is confined between the wall The oil conduits 4| and 42 receive oil from i" the pressure pump 48 (Fig. 1) which is arranged .88 not exerting any mechanical pressure, however, against the Neoprene sealing ring.

Oil enters and leaves the cylinder 55 through an axial port 13 extending upwardly in the mounting block 58 and opening into a passageway 14 extending horizontally in the mounting 5-48, the flexibility, of the conduit 18 accommodating the rise and fall of the mounting block 58 with the ram |8 As shown in Figure 3, the motion of the ball check valve 18 is confined within" a valve cage 18, which also confines the compression spring 8| which bears against the valve, A stud 82 carried by the cage limits the unseating motion of the valve. The cage 19 i held in place in the bore 14 bya set screw 83. Ports 84 and 85 in the body of the-cage," conduct oil from the passageway 13 and from intake port 15 to the right hand endof a coupling tube 88. A Neoprene sealing ring 81 surrounds the reduced right hand end 86a of the coupling tube,

and has its outer surface seating in a counterbore 14a coextensive with the bore 14. The sealing ring 81 is formed with a V-shaped groove 81a is efiective to engagein the V-shaped groove in coupling tube 86 by-a set screw82,

The lefthand end of the coupling tube 88 is adapted to have connection-with the punch 21 through a passageway 94 formed in the punch holder 21. Another Neoprene sealing ring 85,

similar tothe sealing ring 81, has a sealing fit between the reduced left hand end 811) of the coupling tube and a counter-bore 84a extending from bore 84. A confining ring 88, similar to the confining ring 88, loosely confines the sealing ring against objectionable endwise displacement. A bushing 81, similar to the bushing 8|, engages over the left hand portion of the coupling tube and screws into a threaded counterof very slight taper.

' the taper of the punchis such that the side wall thickness at the upper end of the shell is ex-- tremely thin, approximately one half of the side wall thickness at the lower end of the shell.

In the operation of the stripping mechanism, 'oil is supplied to the hydraulic cylinder 55 from pump 48 at pressures typical of the discharge pressures of these gear pumps, 1. e., somewhere between say '10 pounds and 60 pounds per'sduare inch. This pressure is effective on the piston 58 and assists the spring 63 in keeping the hydraulic cylinder distended. This pressure also transmits oil past the check valve '16 and on through the coupling tube 86 to the passageway 98 extending down through the punch 2|. This flow of tion; or the parts may be so proportioned that f interval to perform the entire stripping operathese extremely high pressures are of shorter duration for the purpose of breaking the extremely high-adhesion between the punch and the blank, following which the much lower pressures transmitted'from the pump 48 are utilized tocomplete the final operation of sliding the shell downwardly oil the end of the punch.

It will be evident that my improved hydraulic stripping mechanism exerts no endwise pressure whatever against the extremely thin wall at the upper end of the shell. Hence, there is no stripping mutilation oi the upper end of the shell.

Because it is not necessary tov cut off a substantial portion of the upper end of the shell, as is oil through the punch, occurring before the actual stripping operation, tends to cool the punch and lubricate the punch and blank in the drawing operation. As previously described, this cooling and lubricating flow of oil also occurs through the conduits 4| and 42 for lubricating the outer surface of the blank and for lubricating the forming throat of the die 22 during the drawing operation. As the ram It moves downwardly and the punch 2| forces the blank 23 down through the drawing die 22, the hydraulic cylinder 55.

moves down concurrently with the ram through' an idling travel. As soon, however, as the upper end of the blank 23 has cleared the drawing throat 22a: and is in or below the clearance area- 22y, the striker head Glof the piston 58 strikes the upper surface 33' of the die shoe plate". Thereupon, continued downward movement .of the ram l8 causes relative upward travel of the piston 58 within the cylinder 55 and exerts a tremendous pressure on the oil contained wi usually true when stripping the shell by mechanical stripping mechanism, it follows that a shorter length of draw maybe employed, which means that a shorter length of press or a shorter throw of crank may be used. This is all in addition to the reduced expenditure of enemyinvolved in the shorter length of draw. and the avoidance of the considerable portion of scrap waste which must be cut from the upper end of a mutilated shell. My improved hydraulic stripping mechanism may be employed in the performance of several of the end drawing operations, particu-' larly where theshell has been drawn down to such a thin wall that mechanical stripping mechanism is very likely to damage the upper edge of such thin wall.

While I have illustrated and described what I regard to be a preferred embodiment of themvention, nevertheless it will be understood that.

such is merely exemplary and that numerous modifications and rearrangements may be made 40 therein without departing from the essence of the invention. For example, while the feed of he oil from a positive pressure pump, such as the pump 48, is desired under mostoperating conditions, it will be understood that the oil might be supplied to the cylinder from a gravity head' reservoir, from an air chamber, or from any other I suitable source of supply. The mechanism may the cylinder. It will be evident that it is possi 16 to obtain an extremely high pressure within the cylinder because drawing presses capable of drawing these steel shells have a capacity ranging anywhere from 150 to 350 tons, and any portion of this capacity is available for creating pressure within the cylinder 55 at this instant because the drawing operation on the blank has been completed and no further downward pressure need be exerted on the punch. A pressure ranging from 10 tons'to 20 tons is adequate on the hydraulic cylinder 55 for average working condi tions, these pressures creating fluid pressures in the oil in the neighborhood of 3000 pounds to also be provided with automatically actuated valves for automatically stopping and starting the flowof oil 'atpredetermined times, i. e., for example, to shut off the flow through the punch during the time thatthe ram is is at top dead center whereby the next shell to be drawn can.

be set over the punch without the objection of cooling oil splashing over the parts and over the.

operator. If desired, this automatic valve ar'-. rangemen-t might also be arranged to shut off the die coolant liquid so that the entire volume of the pump 48. would be forced through the punch 2| 6000 pounds per square inch for average working conditions. It will be understood that these pressures and proportions are merely illustrative and the invention is not necessarily limited thereto. These fluid pressures are transmitted through the coupling tube 86 and passageway 98 to the space 99 between the lower end of the punch and the lower end of the shell. pressures are effective to instantly free the shell from the punch, even against the most adverse circumstances of drawing steel shells on punches ortioned with respect to stroke of ram, stroke of hydraulic cylinder, etc., that the extremely is liquid through one of said members, andjhydrau- These extremely, high The parts may be so prowhile the punch is being withdrawn from the shell, 1. e., for about of an inch above lower dead center. Th automatic valve arrangement could be such that both the oil line to the punch and the oil line to the die.would be opened up to the full capacity of the pump after the punch had passed ,the above point, so as to'get the maximum cooling effect of. the-oil on the punch and on the die.

I claim:

1. In a punch press comprisinga reciprocating ram, the combination of punch and die members adapted to be moved toward and from each other by the reciprocation of said ram for drawing a .metallic blank, means for circulating a cooling high pressures generated within the cylinder are I transmitted through the punch. overs. sufllcient lic stripping means for utilizing said liquid to release the blank from said latter member, said hydraulic stripping means comprising a hydraulic cylinder responsive to said ram for creating a momentary high pressure surge in said flow of cooling liquid to release the blank from said member.

- 2. In a punch press comprising a reciprocating ram, the combination 0! punch and die members adapted to be moved toward and from each other by the reciprocation of said ram for drawing a metallic blank, a-pump for circulating a cooling or lubri'cating liquid through said punch member, a hydraulic cylinder responsive to the motionof said ram for creating an augmented preson said ram and adapted to engage a striker surface on said bed to create a high Ydraulic pressurein said cylinder in predetermined timed relation to the completion of the drawing, operation, and means for utilizing the hydraulic pressure created in said'cylinder for stripping the blank from said punch member.

4. In a punch press comprising a reciprocating ram and bed, the combination of punch and die members carried by said ram and bed and adapted to perform a drawing operation on a tubular blank, a hydraulic cylinder and piston carried by said ram and adapted to be relatively actuated when said ram approaches the lower end of its stroke, and a high pressure duct carried by said ram and moving bodily with said hydraulic cylinder, said duct conveying to the punch the hydraulic pressure created in said cylinder for stripping the blank from said punch. j g

i 5. In a drawing press comprising a reciprocating ram and bed, the combination'of punch and die members carried by said ram and bed and adapted to perform 'a drawing operation on a tubular blank, a fluid passageway extending through said punch, a hydraulic cylinder carried by said ram, means for supplying oil to said cylinder, a piston in said cylinder adapted to engage said bed and to cause relative motion between, the cylinder and piston when the ram approaches the bottom of its stroke, whereby to create a large hydraulic pressure in said cylinder substantially at the in-' stant thatthe drawing operation on said blank is completed, and a high pressure conduit moving bodily with said ram for conducting oil under pressure from said cylinder to the passageway in said punch ior stripping the tubular blank from said punch.

6. In a drawing press 01 the class described, the combination 01' a bed, a ram adapted to reciprocate relatively to said bed, a circular die carried by said bed, a punch carried by said ram and adapted to move down through said circular die to perform adrawing operation on a metallic shell, an oil pump, means for conducting cooling and lubrieating oil from said pump to said die and punch, a hydraulic cylinder carried by said ram, a piston within said cylinder projecting from the lower end thereof and adapted to engage a striking surface on said bed when said ram approaches the lower end of its stroke, spring means normally holding said piston at the lower end of its stroke in said cylinder, means for conducting oil from said pump through an inlet port to said cylinder, a check valve at said inlet port preventing return flow from said cylinder to said pump, and means for conducting oil from said cylinder to the lower end of said punch, whereby when said ram approaches the lower end of its stroke substantially at the completion of the drawing operation said piston encounters the striking surface on said bed and creates a hydraulic pressurein said cylinder which is transmitted to the space between the lower end of said punch and the lower end 0! said shell for stripping the shell from said punch.

7. In a drawing press of the class described, the combination of a bed;.a ram adapted to reciprocate relatively to said bed, a circular die carried by said bed,- a punch carried by said ram and adapted (to move down through said circular die to perform a drawing operation on a metallic shell, an oil pump, means for conducting cooling and lubricating oil from said pump to said die and punch, a hydraulic cylinder carried by said ram,

a piston within said cylinder projecting from the lower end thereof and adapted to engage a striking surface on said bed when said ram approaches the lower end of its stroke, means for conducting oil from said pump through an inlet port to said cylinder, a check valve at said inlet port preventing return flow from said cylinder to said pump, and means for conducting oil from said cylinder to the lower end of said punch, whereby when said ram approaches the lower end of its stroke substantially at the completion of the drawing operation said piston encounters the striking surface on said bed and creates a hydraulic pressure in said cylinder which is transmitted to the space between the lower end of said punch and 

